Method and apparatus for grading finely-divided material



H. K. HITCHCOCK.

METHOD AND APPARATUS FOR GRADING FINELY DIVIDED MATERIAL.

APPLICATION FILED AUG-9. I915.

1,319,771. Patented Oct. 28,1919.

3 SHEETSSHEET I.

FIELI.

V INVENTOR WITNESSES H. K. HITCHCOCK METHOD AND APPARATUS FOR GRADINGFINELY DIVIDED MATERIAL.

I APPLICATION FILED AUG.9, 1915. 1,319,771. Patented 001;. 28,1919.

3 SHEETS-SHEET 2.

WITNESSES INVENTOR H. K. HITCHCOCK.

METHOD AND APPARATUS FOR GRADING FINELY DIVIDED MATERIAL.

APPLICATION FILED AUG-9,1915.

1,319,771. Patented 001:. 28,1919.

3 SHEETS-SHEET 3.

u II III! wn'nzssss INVENTOR ww wMM/WW ga /W 2g HALBERT K. HITCHCOCK, OFPITTSBURGH, PENNSYLTTANIA.

METHOD AND APPARATUS FOR Application filed August 9, 1915. Serial No.44,625.

'7 0 all whom it may concern:

Be it known that I, HALBERT K. HITCH- COCK, a resident of Pittsburgh, inthe county of Allegheny and State of'Pennsyl- Vania, have invented a newand useful Improvement in Methods and Apparatus for GradingFinely-Divided Material, of which the following is a specification.

This invention relates to method and ap-' paratus for grading orclassifying finely divided material, such as sand, emery or otherabrasive materials to 'be used, for example, in grinding or polishingplate glass, or as binders in ceramics, or any other finely d1- videdmaterial. The invention is an im- ,provement upon that shown, describedand claimed in my Patent No. 1,100,302, June,

' The object of the invention is to provide improved method andapparatus for producing a cleaner and more accurate separation orclassification of thedifi'erent grades of material and avoidingcontamination of one grade by any other grade; which more particularlyproduces a cleaner coarse. grade" or grades of the material; and whichalso automatically maintains a unlform or constant density of themixture in the grading vessel, so that the grading or classifying'opparticles are between definite upper and lower limits and no materialhaving other characteristics. I

In the drawings, Figure 1 represents a diagrammatic sectional elevationof one form of grading apparatus embodying the invention; Fig. 2 is asimilar view illustrat-' ing the application of the invention togrinding apparatus; Fig. 3 is a view corre-,

sponding to Fig. 2 and illustrating a diflerent form of the invention;and Fig. 4'is a detail sectional elevation of the lower portion of thegrading vessel.

The method utilizes the general principles Specification of LettersPatent.

the finer grades are carried-upwardly by invention being shown herein.

GRADING FTNELY-DIVIDED MATERIAL.

Patented Oct.

set forth in my prior Patent 1,100,302, and grades or classlfies thematerial while in suspension in a liquid in a gradin vessel by theactlon of a current of liquid aving an upward flow or travel relative toa downward movement of the material, which separates and classifies theseveral grades in diflerent strata or zones in said vessel, the finergrades near the top and the coarser grades near the bottom. The material'to be graded has heretofore beenintroduced into the grading vesselelther at its bottom, as in my Patent 1,100,302, or at the upper levelof the liquid therein. When introduced at the bottom the upward flow ortravel of the liquid relative to the material, and pass in turn theoutlets through which the several coarser'grades are withdrawn. Thisgives practically clean grades 1n ordinary grinding apparatus but asmall percentageof the fine material unavoidably passes out through thevarious openings when the apparatus is run c0ntinuously. On the otherhand, when the material 1s introduced at the upper level Ofljqlid in'thegrading vessel it is necessary to allow considerable time for thematerial to settle to the proper level before withdrawing the finergrades, or the finer grades withdrawn are contaminated by some of thecoarser material, which has to pass downwardly through the finer gradesto reach its proper level near the bottom of the vessel.

By my improved method the material to be graded is introduced into thegrading vessel at a level intermediate its bottom and the upper level ofliquid therein, thereby enabling the coarser material to traveldownwardly against the rising current of liquid and the finer grades totravel upwardly with said current, so that all grades of material findtheir proper levels without contaminating one grade with material fromanother. The material to be graded maybe introduced into the gradingvessel in any suitable. manner but preferably is in suspension in aliquid, being conducted to and introduced into the grading vessel in theform of a stream. of mixture which may flow or travel either upwardly ordownwardly, both forms of the The upward flow or travel of the liquidrelative to the material may be produced in any suitable manner,'suchfor example as described in by prior Patents, Nos, 934,441,

September 21, 1909, 1,056,415, March 12}, 1913, and 1,100,302, June 6,1914, that 1s, 1t may be produced by the displacement of the liquid bythe solid particles travellng downwardly, the displaced liquid rising totake the place of the falling particles and thereby creating an upwardflow of travel of the liquid, or it may be produced by mtroducing asupply of liquid into or near the bottom of the grading vessel. Th1s lquid, for ex-- ample, may be that WlllCh carrles 1n suspension theparticles of material to be graded, the liquid having an upward fiow ortravel through the grading vessel to the overflow at the top, while theparticles of material to be graded or classified have a downwardmovement relatively to the upward flow of the liquid and seek the levelsof their proper grades in said vessel. The best results, however, areobtained when the upward flow or travel of the liquid is produced oraugmented by introducing a separate supply of fresh liquid into thegrading vessel at or near its bottom and preferably at a level below thelevel at which the material to be graded is introduced thereinto. Thisfresh liquid supplv has an upward flow or travel relative to thedownward movement of the coarser particles of material to be classifiedand accurately separates or classifies the same into definite grades.The outlet or outlets for the coarsest grade or grades may be located atany suitable level, but are preferably located at a level between theinlet for the fresh liquid supply and the inlet for the material to begraded, so that they lie in a zone or stratum not traversed by any ofthe finer grades. Consequently, an extra clean coarse grade or gradescan be withdrawn from this region of the grading vessel. The freshliquid supply travels upwardly through the grading vessel with theliquid of the mixture containing the abrading material, but the velocityof the upward flow or travel of the liquid relative to the downward flowof the material at and near the inlet for the mixture is not sufiicientto carry any of the coarser particles upwardly, but is merely sufficientto lift the finer grades to their proper levels in the grading vessel.

The mixture of liquid and finely divided material to be classified ispreferably introduced into the grading vessel in an upwardly travelingstream, but may be introduced in the form of a stream of mixture havinga downward flow or travel relative to the upward flow or travel of themixture in the grading vessel, and which stream of material is sohandled as to be independent of the main body of liquid in the gradingvessel, say for example, by introducing it through a downwardlyextendingpipe or conduit dipping into the mixture in the grading vesseland having its lower end immersed therein to a level above the level ofthe outlet for the coarsest grade withdrawn therefrom. The density ofthe mixture in the grading vessel varies from time to time as the totalquantity of material therein to be graded increases or diminishes, andthe total quantity of material in the grading vessel varies with thesupply thereto and the amounts of the various grades withdrawn at thedifferent outlets. While the downwardly moving stream of mixtureintroduced into the grading vessel is independent of or separated fromthe body of liquid therein, nevertheless the density of the body ofmixture in the grading vessel affects the velocity of the flow of thestream of mixture being supplied tosaid vessel. This is due to the factthat the column of mixture in v the pipe or conduit through which it isintroduced into the grading vessel is balanced against a similar columnof the body of mixture in the grading vessel. If the weight or pressureproduced by the body of the mixture in the grader is less than that ofthe column of liquid in the pipe or conduit the preponderating weight ofthe mixture in the pipe or conduit produces a more rapid downward flowthereof, while, on the other hand, if the weight or pressure produced bythe mixture in the grading vessel is greater than that in the pipe orconduit through which the mixture is introduced thereinto, then thepreponderating effect of the body of liquid in the grading vesseltendsto .produce an upward flow of the mixture in the pipe 'or conduit.This effect partially or completely counteracts the normal downward flowof the mixture in the delivery pipe or conduit to replace the mixturebeing withdrawn from the grading vessel and causes more or less of themixture being supplied to the grader to pass out through the overflowand back to the sump, thus shunting the superfluous material around thegrader. Consequently the velocity of the downward flow or travel of themixture through the delivery pipe or conduit varies inversely with thedensity of the body of the mixture in the grading vessel, increasing asthe density decreases and decreasing as the density increases, and has atendency to automatically govern or regulate the mixture being graded sothat it is maintained at a practically uniform or fixed density.

Referring to the drawings, Fig. 1 repre sents the invention applied toapparatus for grading or classifying finely divided material. In manyrespccts the apparatus shown is similar to that of my rior Patent1,100,302 before referred to. s illustrated, it comprises aprimarygrading vessel or tank 10 provided with a bottom inlet pipe 11through which a fresh liquid supply may be introduced for producing theupward flow or travel of the liquid for the grading operation, and alsowith an overflow outlet 12 through which the excess liquid. and mud andthe material too fine for further use flow. to the sewer. In saidprimary'grader the particles of materialare distributed in'vari ousstrata orzones'accordmg to the characto be collected for use or to beground up into vessel.

'sels for each grade withdrawn.

smaller sizes if necessary, but preferably each grade is conducted insuspension in the liquid to an independent secondary grading vessel ortank 19, there being one of said yes- Said vessels 19 are each providedwith a bottom 'inlet' 20 for a clear liquid supply, and with an overflow21 to carry off the fine material either to the sewer or to a sump orpit to be later regradedf The secondary cones 19 are of the sameconstruction shown in my prior-Patent 1,100,302, embodying a conicallower portion 22, a cylindrical intermediate portion 23 and a conicalupper portion The upward velocity at the top of the comcal bottom shouldbe slightly above the upward velocity in the primary grading cone at thepoint from which the material con; ducted to the secondary grader comes,while the.- upward velocity in the space in the cylindrical part of thegrader should be'the same as the upward velocity at the point in theprimary cone where the next finer grade is withdrawn. The opening to theoutlet,

pipe or conduit 25 from each secondary grading vessel is at a level ator near the bottom of the cylindrical intermediate portion 23 of saidvessel, so that a clean grade of material is withdrawn therefrom, saidmaterial being conducted to a storage tank 26, in which it may be heldin suspension for use as desired, or may be allowed to settle for lateruse.

The material to be graded is supplied to the primarygrader from a mixingtank or lixivia-tor 30, in which. are located power driven paddles orstirrers 31 for mixing the material and putting it in suspension in theliquid. The liquid is introduced to said tank through a suitable pipeand the solid material to be graded may be shoveled in or delivered froma hopper, as desired. The material'in suspension in the liquid flowsfrom he tank 30 through a pipe 32 into a mixin cone or funnel 33, fromwhich it passes to the primary grader through a depending pipe orconduit 34 connected to the bottom of the cone 33 and extending downinto the mixture in the primary grading The outlet from the lower' endof the pipe 34 may be atany suitable level intermediate the bottom ofthe grader 10 and the outlet" pipes. or conduits 13'and 14 maintaining aconstant head of the mixture Preferably; suitable-means isprovided for Yshown as at a level between the openings beingsupplied to the primarygrader, land 1 in the, form shown the supply of material to the cone 3 3is. regulated by a ball 'float 3'5 in said cone, which controls a" valve36 in the-plpe 32. This ball float. maintainsa definite level of liquidinthe mixing cone 33 and mcreases'the supply through the valve 36 as thelevel of liquid falls and decreases it as the level of liquid rises.

The depending delivery pipe34 automati cally maintains substantially auniform den.-

sity of the mixture in the primary grading vessel with the severalgrades to-be withdrawn therefrom at substantially constant levels. Asthe density of the body of the mixture in the primary grading vesselincreases there isan'increa'sing tendency to counteract or retard thedownward flow or travel of the mixture being delivered to said primarygrader through the pipe 34, and if an over supply of material collectsin the D primary grading vessel further supply of' material from thelixiviator 30 is held back until turther material is withdrawn fromtheprimary grader through the several outlets therefrom. If the densityof the material in the primary grading vessel decreases by insuflicientsupply or too rapid withdrawal of the several grades therefrom'theoppositlon to the downward flow or-travel of'the mlxture through thepipe 34 decreasesand a greater supply of material passes through thelixiviator to the primary grading vessel.

This arrangement produces a senes. of very clean definlte grades ofmaterial with practlcally unvaryl'ng characteristics in each of theseveral grades as soon as the grader ,has operated long enough to reacha stable condition. I

F1g.,2 illustrates the invention applied for gradlng finely dividedmaterial, such as sand or the like, and supplying the same directly to agrinding apparatus. In the apparatus shown 40 represents the grindingtable equipped with the usual runners 41 and surrounded by a gutter 42leading to the ditch-.43 through which the used materlal flows to the.s'ump or pit 44, provided with the usual waste overflow 44 to thesewer, .for eliminating the excess water and 45 having a plurality ofwithdrawal pipes 46, 47, 48, the inlets to which are at different levelsn sand vessel, said pipes being provided vwlth suitable valve mechanismenabling material to be delivered from any one or more of said pipes toa trough 49 through whlch 1t flowsto the grinding table. An

overflow pipe 39 conducts the waste material from the grader 45 to theditch 42. So far whose bottom opening 1s immersed in the liquid in saidvessel at a level intermediate the levels of the openings to the outletpipes 46 and 47. The bottom of the grading vessel is provided with aninlet 51 for a clear liquld supply to produce or augment the upward flowor travel of the liquid relative to the material. The coarse partlclesin the material to be graded passing in through the pipe 50 falldownwardly against the rising current from the inlet 51, the velocity ofsaid current being sufliclent to lift the finer particles of materialbefore they have a chance to fall to the outlet for the coarsest grade.clean, coarse grade of material may be withdrawn from the pipe 46. Thefiner grades rise to the levels of the outlets for the finer grades, butno coarse material is carried up with the fine, so that the severalfiner grades are clean and free from contamination by the coarsergrades.

The material to be graded is supplied to the pipe 50 from a supply boxor vessel 52, located at the upper end of the pipe 50 and provided witha suitable hand-operated valve 53 for allowing or shutting off the flowof material from said vessel to the pipe 50. Material is supplied tosaid vessel in any suitable manner,'such as by a centrifugal pump 54,the inlet to which dips into the sump or pit 44, and which pump suppliesmaterial to the vessel52 through the pipe 55. Vessel 52 is also suppliedwith an overflow pipe 56 delivering to the sump and connected to saidvessel 52 at -a level above the valve 53, so that when said valve isopen a constant head or level of liquid is maintained in the vessel 52at the level of the overflow pipe 56. v

In operation of this system the valve 53 is open and the materialdelivered by the pump passes downwardly to the grading vessel 45 throughthe pipe 50, the excess flowing back to the sump through the overflow56. The absolute density of the body of the mixture always depends uponthe exact head of the overflow 56 above the level of liquid in thegrading vessel, which head is constant and produces the downward flow ofthe supply of material to the grader.-

The vertical depending pipe 50 with its opening below the level of theliquid in the tank 45 automatically regulates the flow of material tothe grading vessel in accordance lation of the supply of material toConsequently a very with variations in the density of the mixture insaid vessel, as before described, and it also produces very clean gradesof material at the different levels in the grading vessel. so that thegrinding operation is more efi'ectlVe and may be carried on with greaterrapidity. Throughout the grading operation material m' y be dischargedto the grinding table with the several grades in any desired order orsequence and constantly in suspension in a liquid, and furthermore, thematerial flowing off from the grinding table passes back to the sumpand-again up to the grading vessel, so that a complete cycle ofcirculation is going on during the entire grinding operation. Freshcoarse material is added from time to time to the sump, usually a newmeasured batch before each grinding operation.

Figs. 3 and 4 illustrate another arrangement for securing very cleangrades of ma-' terial at the different levels in the grading tank, butwhich omits the automatic reguthe gradlng vessel in accordance with thedensity of the material therein. Tn this form the circulation of thematerial to and from the grinding table is the same as in the formbefore described, the material passing out from the grading vesselthrough the several outlets 46, 47, 48 to the grindin table, thence tothe sump and thence back 1nto the grading vessel. The material isdeliveredfrom the sump to the grading vessel 45 by a centrifugal pump54, which discharges into the grading vessel through a'nozzle 60 at thebottom of said vessel and which extends part way up into the same, itsoutlet 61 being at a level above the level of the opening to thewithdrawal pipe 46 for the coarsest grade of material. I The gradingvessel is also provided at or near its extreme bottom, and at a levelbelow the level of the outlet for the coarsest grade, with an inlet 62for a supply of clear liquid. The .finer particles delivered to thegrading vessel by the nozzle 60 pass directly upwardly to their variouslevels in the grading vessel, and as no coarse material passes throughthe levels of the finer grades the latter are withdrawn in a cleancondition uncontaminated by the coarser material. The coarse materialfalls downwardly from the outlet 61 against the rising stream of clearliquid from the inlet 62. This rising stream prevents any of the finergrades from flowing through the outlets for the coarse grade or grades,so that a very clean, coarse grade of material is withdrawn from thisregion in the grading vessel. The auxiliary water supply also enablesthe operator to control the density of the grinding mixture withoutchanging the velocity of flow from the pump or appreciably varying thegrading velocity for the finer grades.

Inbothof thefsystem's shownrespectively in Figs; 2 and 3v the finishingoperation is carried on with the finer grades collected in the upperstrata of thegrading. vessel dur- 1. The method of grading finely dividr material mixed with a liquid, consisting in subjecting said materialin a vessel to an upward flow or travel of the liquid relative to thematerial and thereby separatln the material into grades, withdrawinerent grades from said vessel indepen ently and from difi'erent' levelstherein, introducing the material "to be graded into said vesseltherefrom,

at a level above the level of the coarsest grade and below the level ofthe next finest grade withdrawn therefrom, and simultaneouslyintroducing liquid into sa1d vessel below the level from which thecoarse ma;- terial is withdrawn.

2. The method of grading finely divided material mixed with a liquid,consisting in subjecting said material in a vessel to an upward flow ortravel of the liquid relative to the material and thereby separating thematerialvinto grades, introducing sa1d material in suspension in aliquid into said vessel at a level intermediate the levelsof the'coarsest and useful finest grades withdrawn simultaneously withdrawingcoarse useful material from a level below and fine material from a levelabove the level at which the material is-introduced to said vessel, andsimultaneously introducing liquid into said vessel at a level below thelevel at which the material introduced thereto.

3. The method of grading finely divided material mixed with a liquid,consisting in subjecting. said material in a vessel to an upward flow ortravel of the liquid relative to the material and thereby separating thematerial into grades, introducing said material under a constant head insuspension in a liquid into said vessel at a level intermediate thelevels of the coarsest and finest grades withdrawn therefrom by adownwardly moving stream of mixture independent of the upward flow ortravel of the liquid in said vessel, to thereby control the flow of saidstream by the density of the mixture-in said vessel, and withdrawingseveral grades from said vessel separately and independentl L The methodof grading finely divided material mixed with a liquid, consisting insubjecting said material in a; vessel to an upward flow or travel of thellquid relative the material and thereby" separating the materlal mtogrades, introducing said ma- I i a;

terial under aconstant' hea'd. suspensionma l1qu1d mto said vessel at alevel intermediate the levels, of the coarsest and finest gradeswithdrawn therefrom by a downwardly moving stream of mixture independentof the upward flow or travel-of the liquid 1n sa1d vessel, to therebycontrol the flow of sa d'streamdby the denslty o fthe mixture in sa1dvessel-,Etnd withdrawing coarse mater al from a level-below and finematerial from a level above the level at which the material isintroduced into said vessel. T

The method of grading finely divided material mixed with a liquid,consisting in 1 subjecting said material in a vessel toan upward flow ortravel of the liquid relative to the' ma ter1al, and therebyseparating'the material into grades, introducing the maintermediatethelevels of the coarsest and finest grades withdrawn therefrom,simultaneously withdrawing a coarse grade from said vessel at a levelbelow the level at which tive to the material to separate the materialinto grades, means for independently withdrawing diflerent grades from-diflerent levels in sa1d vessel, means for introducing 'terial to begraded into said vessel at a level the material is introduced thereto,withthe material to be graded into said vessel at a level intermediatethe level of the coarsest and next finest grades withdrawn therefrom,and means for simultaneously introducing liquid into said vessel belowthe level from which the coarse material is withdrawn.

7. Apparatus for grading finely divided material mixed with a liquid,comprising a grading vessel, means for producing therein an upward flow:or travel of the liquid relative to the material, means for withdrawingseveral different grades from dilferent levels in said vessel, a conduitfor supplying material to be graded extending into said vessel andterminating at a level intermediate the levels of the coarsest and Ifinest grades withdrawn therefrom, and means for introducing a liquid.supply to said vessel at a level below. the level of the coarsestmaterial withdrawn therefrom.

8. Apparatus for grading finely divided material mixed with a liquid,comprising a grading vessel, a conduit for supplying material to begraded in suspension in a liquidjto said, vessel, said conduit openinginto rfiow, means for returning the material from said overflow to thevessel for regradmg, an

outlet for withdrawing the coarse material from the vessel at a levelbelow that at which the material is introduced therelnto, and outletsfor Withdrawal of the finer material at levels above that at which thematerial is introduced thereinto.

9. Apparatus for. grading finely divided material mixed with a liquid,comprising,

a grading vessel, a conduit, for supplying material to begraded insuspension in a liquid to said vessel, said conduit opening into saidvessel at a level intermediate its bottom and the upper level of theliquid therein, said vessel being provided with an overflow, means forreturning the material from said overflow to the vessel for regrading,outlets for withdrawing the coarse material from a level below, andoutlets for withdrawing the fine material from levels above that atwhich the material is introduced into the vessel, and a liquid supplypipe connected to said vessel at a level below that at which thecoarsest material is withdrawn.

10. Apparatus for grading finely divided material mixed with a liquid,comprising a grading vessel, means for producing therein an upward fiowor travel of -the liquid relative to the mate-rial, outlets forwithdrawing the various grades from difierent levels in said vessel, anoverhead supply reservoir for material to be graded mixed with water, aconduit extending downwardly therefrom into said reservoir andterminating at a level intermediate the levels of the coarsest andfinest grades withdrawn therefrom, and a liquid supply to said vessel ata level below the level of the coarsest material Withdrawn therefrom.

11. Apparatus for gradin finely idivided material mixed with a liquicomprising a grading vessel, means for producing therein an upward flowor travel of the liquid rela tive to the material, outlets forwithdrawing the various grades from different levels in said vessel, anoverhead supply reservoir for material to be graded mixed with water, aconduit extending downwardly therefrom into said reservoir andterminating at a level intermediate the levels of the coarsest andfinest grades withdrawn therefrom, means to maintain a constant head ofliquid in said supply reservoir, and a liquid supply to said vessel at alevel below the level of the coarsest material withdrawn therefrom.

In testimony whereof I have hereunto set my hand.

HALBERT K. HITCHCOCK. Witnesses:

ELBERT L. HYDE, GLENN H. LERESCHE.

